These echoes last up to 1 s (much longer than classic visual-evoked potentials)

The echoes are tied to the occipital alpha rhythm but enhanced by attention

The alpha rhythm may serve a role in maintaining sensory representations over timeRufin VanRullen & James S.P. Macdonald (2012).:

From Stroboscope to Dream Machine: A History of Flicker-Induced Hallucinations
When early neurophysiologists, like William Grey Walter (1910–1977), started using intermittent photic driving in electroencephalography, they were struck by a wide range of visual hallucinations that were reported. In current neuro- science, the phenomenon is used mainly to model hallucina- tions that are related to altered neuronal activity between the thalamus and the visual cortex, such as the Charles Bon- net syndrome. However, during the psychedelic 1960s, Brion Gysin (1916–1986), a painter and a poet, became interested in the hallucinations and designed his own stroboscope or dream machine, as a means for spiritual enlightenment. This article traces back the history of flicker-induced hallucina- tions from the early use of stroboscopes in neurophysiology
B.C. ter Meulena D. Tavya B.C. Jacobsb (2009).:Lucid Dreaming: A State of Consciousness with Features of Both Waking and Non-Lucid Dreaming
The goal of the study was to seek physiological correlates of lucid dreaming. Lucid dreaming is a dissociated state with aspects of waking and dreaming combined in a way so as to suggest a specific alteration in brain physiology for which we now present preliminary but intriguing evidence. This study shows that the unusual combination of hallucinatory dream activity and wake-like reflective awareness and agentive control experienced in lucid dreams is paralleled by significant changes in electrophysiology.
Ursula Voss, PhD (2009).: